Technetium-99m sestamibi myocardial imaging: same-day rest-stress studies and dipyridamole

Development and evolution of nuclear cardiology and cardiac PET in Canada

Gated radionuclide angiography and myocardial perfusion imaging were developed in the United States and Europe in the 1970's and soon adopted in Canadian centers. Much of the early development of nuclear cardiology in Canada was in Toronto, Ontario and was quickly followed by new programs across the country. Clinical research in Canada contributed to the further development of nuclear cardiology and cardiac PET. The Canadian Nuclear Cardiology Society (CNCS) was formed in 1995 and became the Canadian Society of Cardiovascular Nuclear and CT Imaging (CNCT) in 2014. The CNCS had a major role in education and advocacy for cardiovascular nuclear medicine testing. The CNCS established the Dr Robert Burns Lecture and CNCT named the Canadian Society of Cardiovascular Nuclear and CT Imaging Annual Achievement Award for Dr Michael Freeman in memoriam of these two outstanding Canadian leaders in nuclear cardiology. The future of nuclear cardiology in Canada is exciting with the expanding use of SPECT imaging to include Tc-99m-pyrophosphate for diagnosis of transthyretin cardiac amyloidosis and the ongoing introduction of cardiac PET imaging.

The effects of pharmacological interventions, exercise, and dietary supplements on extra-cardiac radioactivity in myocardial perfusion single-photon emission computed tomography imaging

Myocardial perfusion imaging (MPI) as an imaging modality plays a key role in the monitoring of patients with cardiovascular disease. MPI enables the assessment of cardiovascular disease, the effectiveness of therapy, and viable myocardial tissue. However, MPI suffers from some downfalls and limitations, which can influence its clinical applications. These limitations can arise from the patient's condition, equipment, or the actions of the technologist. In this review, we mainly focused on the different effective parameters on radioactivity uptake of organs including liver, intestines, stomach, and gall bladder and how they affect the quality of the acquired images in nuclear medicine. More importantly, we cover how different suggested medicines, foods and exercise alleviative this problem.

Myocardial Perfusion and Ventricular Function Assessed by SPECT and Gated-SPECT in End-Stage Renal Disease Patients before and after Renal Transplant

BACKGROUND

Cardiovascular disease is a major cause of morbidity and mortality in end-stage renal disease (ESRD). Renal transplant is known to improve left ventricle hypertrophy and systolic dysfunction in selected groups of patients.

METHODS

We assessed myocardial perfusion, wall motion and functional parameters by single photon emission computed tomography (SPECT) and Gated-SPECT in 30 consecutive ESRD patients with normal coronary angiograms before and after renal transplantation.

RESULTS

Uremic cardiomyopathy improved significantly after the transplant. The proportion of patients with angina decreased from 26 to 0%; the frequency of cardiomegaly decreased from 57 to 20% (p <0.01); the frequency of segments with perfusion defects decreased from 42.7 to 10.2% (p <0.001); the proportion of patients with low left ventricular ejection fraction (LVEF) dropped from 53.3 to 20% (p <0.001); and mean LVEF increased from (48.0 +/- 9.7% to 58.2 +/- 8.2%). Similarly, the proportion of segments showing systolic wall thickening, hypokinesia and dyskinesia also decreased significantly after renal transplant (p <0.01).

CONCLUSIONS

Uremic cardiomyopathy may be potentially reversible in patients with normal angiographic coronary arteries after renal transplant in a relatively short period of time. SPECT and Gated-SPECT are objective gateway methods to determine myocardial perfusion, hypokinesia, dyskinesia, and functional parameters (left ventricular ejection fraction and systolic wall thickening) and may be useful to establish diagnostic, coronariographic, prognostic, and therapeutic indications.

Usefulness of rapid low-dose/high-dose 1-day 99mTc-sestamibi ECG-gated myocardial perfusion single-photon emission computed tomography

BACKGROUND

The clinical usefulness of a rapid rest low-dose/stress high-dose (dose ratio =1:5) (99m)Tc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT) protocol for the detection of coronary artery disease was evaluated.

METHODS AND RESULTS

In 89 patients, rest images were obtained immediately after the injection of (99m)Tc-sestamibi (256.1+/-28.4 MBq) followed by drinking water (400 ml). Exercise or vasodilator stress test was performed immediately after the completion of rest imaging with the injection of (99m)Tc-sestamibi (1312.3 +/-167.6 MBq). Prior to the post-stress imaging, patients were asked again to drink water (400 ml) in order to eliminate subdiaphragmatic tracer activity. The myocardial count ratio (stress/rest) of (99m)Tc-sestamibi was calculated. Image quality was scored using a 4-point scale system (4= excellent, 3= good, 2= poor, 1= unacceptable). Coronary angiography was performed in 56 patients within 1 month of the SPECT scan. All patients successfully performed the protocol and total examination time was 108+/-7 min. The myocardial count ratio of (99m)Tc-sestamibi was always greater than 6. The image quality was satisfactory both at rest (3.4+/-0.9) and after stress (3.9+/-0.2). The sensitivity and specificity to detect coronary artery stenosis >50% was 84% and 97%, respectively.

CONCLUSIONS

This rapid one-day (99m)Tc-sestamibi protocol provides adequate image quality and diagnostic accuracy for detecting coronary artery disease.

Visual assessment of left ventricular perfusion and function with electrocardiography-gated SPECT has high intraobserver and interobserver reproducibility among experienced nuclear cardiologists and cardiology trainees

BACKGROUND

Stress electrocardiography (ECG)-gated single photon emission computed tomography (SPECT) for assessment of left ventricular perfusion and function improves the confidence of interpretation and enhances specificity for detection of coronary artery disease. The reproducibility of visual interpretation of ECG-gated SPECT images and the significance of training and experience have not been reported previously in a large series of consecutive patients. We evaluated both intraobserver and interobserver agreement of interpretation of ECG-gated SPECT images among 3 cardiology trainees and 3 experienced nuclear cardiologists from 3 institutions.

METHODS AND RESULTS

Three nuclear cardiologists and 3 cardiology trainees who had fulfilled American College of Cardiology/American Society of Nuclear Cardiology Core Cardiology Training Symposium (ACC/ASNC COCATS) guidelines for level II training in nuclear cardiology independently evaluated 106 consecutive technetium 99m sestamibi SPECT images with ECG gating of either the stress or rest images. All cases were interpreted blindly, twice in random sequence, without clinical data. We assessed intraobserver and interobserver agreement for myocardial perfusion, left ventricular regional and global systolic function, and overall clinical impression, by means of percent agreement and Cohen's kappa statistic. Intraobserver agreement was good (82%-92%, kappa = 0.54-0.84) for assessment of myocardial perfusion, systolic function, and overall impression. Interobserver agreement was also good, ranging from 65% to 90% (kappa = 0.32-0.76), with better agreement found for assessment of function (77%-85%, kappa = 0.52-0.7) than for perfusion (65%-80%, kappa = 0.32-0.6). For all measures, there were no significant differences in reproducibility between nuclear cardiologists and cardiology trainees.

CONCLUSIONS

Interpretation of ECG-gated SPECT images has high reproducibility and agreement among both nuclear cardiologists and cardiology trainees.

Exercise supplementation to dipyridamole prevents hypotension, improves electrocardiogram sensitivity, and increases heart-to-liver activity ratio on Tc-99m sestamibi imaging

BACKGROUND

Myocardial perfusion imaging with dipyridamole is an alternative with which to evaluate patients who are unable to exercise. Many patients who undergo dipyridamole testing are limited in their ability, but are not completely unable, to exercise. There are benefits from adding low workload exercise to dipyridamole testing, including a reduction of thallium 201 concentration in the liver, leading to a higher heart-to-liver activity ratio and better image quality. This prospective study was designed to evaluate a protocol of exercise supplementation during dipyridamole technetium 99m sestamibi imaging and to verify whether a higher heart-to-liver activity ratio could be obtained. We also evaluated the potential of this combined protocol to prevent hypotension and induce ischemic changes on the electrocardiogram (ECG).

METHODS AND RESULTS

Ninety consecutive patients who were not completely disabled for exercise underwent dipyridamole Tc-99m sestamibi cardiac single photon emission computed tomography with a protocol of exercise supplementation (DipEx). The heart-to-liver activity ratio, hemodynamics, and electrocardiographic changes were studied. The findings were compared with those of a control group (Dip) composed of 99 patients who underwent dipyridamole infusion alone. Patients with left bundle branch block, pacemaker, and atrial fibrillation were excluded. The DipEx patients tolerated the protocol, exercising 4.2 +/- 1.3 minutes on the treadmill (Bruce protocol). Compared with Dip, patients in the DipEx group had a higher heart-to-liver activity ratio (1.3 +/- 0.4 vs 1.6 +/- 0.5, respectively; P =.00001), had no incidence of hypotension (6% vs 0%, respectively; P =.03), and had a higher sensitivity of the ECG to detect ischemia (6% vs 34%, respectively; P =.003). The increase in sensitivity seen in the DipEx group was accompanied by a significant decrease in specificity compared with the Dip group (67% vs 100%, P =.000001).

CONCLUSIONS

Our data show that the addition of limited exercise to dipyridamole results in benefits during Tc-99m sestamibi imaging, increasing heart-to-liver activity ratio, preventing vasodilator-induced hypotension, and improving ECG sensitivity for the detection of ischemia. Furthermore, this protocol also provides an estimation of the patient's physical capacity and could be used as an alternative for patients undergoing dipyridamole infusion who are not completely unable to exercise.

Right ventricular ischemia in patients with primary pulmonary hypertension

OBJECTIVES

The goal of this study was to determine whether right ventricular (RV) ischemia is a contributory factor in the development of RV dysfunction in patients with primary pulmonary hypertension (PPH).

BACKGROUND

Patients with advanced PPH develop RV dysfunction, characterized by a decreased cardiac output, increased right atrial pressure (RAP) and/or elevated RV end-diastolic pressure, which progresses to heart failure and death. The cause of this dysfunction is unknown. Right ventricular ischemia may play a role in its development.

METHODS

From 1992 to 1999, a prospective study involving 23 patients with PPH at the Instituto Nacional de Cardiologia "Ignacio Chavez" (Mexico City, Mexico) was undertaken. These patients were evaluated clinically and further studied by echocardiography, right heart catheterization and stress myocardial scintigraphy using technetium 99m sestamibi.

RESULTS

Nine patients of 23 were found to have scintigraphic images consistent with RV ischemia. Significant correlation was found between RV ischemia obtained through myocardial perfusion scintigraphy and elevation of RV end-diastolic pressure (p < 0.001), elevation of RAP (p < 0.037) and a decrease in mixed venous oxygen saturation (p < 0.0001). No other clinical or hemodynamic variables showed a significant correlation with RV ischemia.

CONCLUSIONS

A direct correlation exists between RV ischemia, as determined by myocardial scintigraphy, and hemodynamic alterations suggestive of RV dysfunction in patients with PPH.

Enhanced detection of reversible perfusion defects by Tc-99m sestamibi compared to Tc-99m tetrofosmin during vasodilator stress SPECT imaging in mild-to-moderate coronary artery disease

OBJECTIVES

We prospectively compared dipyridamole single-photon emission computed tomography (SPECT) imaging with Tc-99m sestamibi and Tc-99m tetrofosmin for the detection of reversible perfusion defects in patients with mild-to-moderate coronary artery disease.

BACKGROUND

Tc-99m tetrofosmin has a lower first-pass myocardial extraction fraction compared to Tc-99m sestamibi and thus could underestimate mild perfusion defects.

METHODS

Eighty-one patients with 50% to 90% stenosis in one or two major epicardial vessels without previous myocardial infarction, and seven with <5% probability of coronary artery disease underwent dipyridamole SPECT imaging with both agents. The SPECT data were analyzed quantitatively.

RESULTS

Tc-99m sestamibi detected reversible perfusion defects in a greater number of segments (total 363 and 285, p < 0.001, and mean +/- SD, 2.2 +/- 3.0 and 1.8 +/- 2.5 per patient, p = 0.008, for Tc-99m sestamibi and Tc-99m tetrofosmin, respectively), demonstrated a larger extent of perfusion defect (mean +/- SD, 15.8% +/- 12.3% and 12.0% +/- 11.4%, p < 0.03, for Tc-99m sestamibi and Tc-99m tetrofosmin, respectively) and more often correctly identified patients with disease in more than one coronary artery (p = 0.02). There was better defect contrast with Tc-99m sestamibi (defect/normal wall count ratios were 0.60 +/- 0.15 vs. 0.73 +/- 0.14 for Tc-99m sestamibi and Tc99m tetrofosmin, respectively, p = 0.01, for reversible defects seen in identical segments with both agents; and 0.73 +/- 0.16 vs 0.79 +/- 0.17, respectively, p <0.01, for reversible defects detected with either agent alone). There was no significant difference in diagnostic sensitivity or image quality.

CONCLUSIONS

These differences between two commonly used tracers may have significant diagnostic and prognostic implications.

Dobutamine-atropine stress echocardiography and dipyridamole sestamibi scintigraphy for the detection of coronary artery disease: limitations and concordance

OBJECTIVES

We sought to compare dobutamine-atropine stress echocardiography (DASE) and dipyridamole Technetium 99-m (Tc-99m) sestamibi single photon emission computed tomography (SPECT) scintigraphy (DMIBI) for detecting coronary artery disease (CAD).

BACKGROUND

Both DASE and DMIBI are effective for evaluating patients for CAD, but their concordance and limitations have not been directly compared.

METHODS

To investigate these aims, patients underwent multistage DASE, DMIBI and coronary angiography within three months. Dobutamine-atropine stress echocardiography and stress-rest DMIBI were performed according to standard techniques and analyzed for their accuracy in predicting the extent of CAD. Segments were assigned to vascular territories according to standard models. Angiography was performed using the Judkin's technique.

RESULTS

The 183 patients (mean age: 60 +/- 11 years, including 50 women) consisted of 64 patients with no coronary disease and 61 with single-, 40 with two- and 18 with three-vessel coronary disease. Dobutamine-atropine stress echocardiography and DMIBI were similarly sensitive (87%, 104/119 and 80%, 95/119, respectively) for the detection of CAD, but DASE was more specific (91%, 58/64 vs. 73%, 47/64, p < 0.01). Sensitivity was similar for the detection of CAD in patients with single-vessel disease (84%, 51/61 vs. 74%, 45/61, respectively) and multivessel disease (91%, 53/58 vs. 86%, 50/58, respectively). Multiple wall motion abnormalities and perfusion defects were similarly sensitive for multivessel disease (72%, 42/58 vs. 66%, 38/53, respectively), but, again, DASE was more specific than DMIBI (95%, 119/125 vs. 76%, 95/125, respectively, p < 0.01). Dobutamine-atropine stress echocardiography and DMIBI were moderately concordant for the detection and extent of CAD (Kappa 0.47, p < 0.0001) but were only fairly (Kappa 0.35, p < 0.001) concordant for the type of abnormalities (normal, fixed, ischemia or mixed).

CONCLUSIONS

Dobutamine-atropine stress echocardiography and DMIBI were comparable tests for the detection of CAD. Both were very sensitive for the detection of CAD and moderately sensitive for the extent of disease. The only advantage of DASE was greater specificity, especially for multivessel disease. Dobutamine-atropine stress echocardiography may be advantageous in patients with lower probabilities of CAD.

[Nuclear cardiology: technical bases and clinical applications]

Although the role of nuclear cardiology is currently well consolidated, the addition of new radiotracers and modern techniques makes it necessary to continuously update the requirements, equipment and clinical applications of these isotopic tests. The characteristics of the radioisotopic drugs and examinations presently used are explained in the first part of this text. In the second, the indications of them in diagnostic and prognostic evaluation of the different coronary diseases are presented.

Radionuclide imaging of the heart

Nuclear cardiology is an established part of diagnosis and assessment of patients with possible heart disease, the two most common tests being myocardial perfusion imaging and radionuclide ventriculography. Myocardial perfusion imaging comprises approximately 75% of nuclear cardiology studies in the UK, and is used in diagnosis and management of coronary artery disease.

Comparison of dipyridamole stress echocardiography and perfusion scintigraphy for cardiac risk stratification in vascular surgery patients

Dipyridamole single-photon emission computed tomography (SPECT) has a high negative predictive value for perioperative cardiac events, but events are infrequent in patients with a positive test. In contrast, dipyridamole echocardiography is more selective for detection of multivessel disease and thus may have a greater specificity for cardiac events. We therefore compared the ability of dipyridamole SPECT and echocardiography to predict perioperative and long-term cardiac events in 133 patients referred for vascular surgery. The group was also evaluated based on clinical features and ejection fraction. Four patients had surgery cancelled because of high risk and were excluded from further analysis. Among the 129 remaining patients, 21 had coronary revascularization (n=12) or an early cardiac end point (n=9). The sensitivity of SPECT for the prediction of early events (90%) was not significantly different from that of echocardiography (66%, p=NS). The specificity of SPECT (68%) was less than that of echocardiography (88%, p <0.001%), as was the accuracy (72% vs 84%, p=0.02). These findings were replicated after exclusion of patients with treatment end points. During long-term follow-up, 12 patients experienced > or = 1 event: 6 died from cardiac causes, 4 underwent revascularization, and 3 had myocardial infarction. Thus, the specificity of SPECT and echocardiography for late events were 58% and 80%, respectively (p <0.001). The 3-year survival of patients without ischemia during echocardiography or at SPECT was not different (93% vs 94%, p=NS).

Quantitative analysis of myocardial ischemia by technetium-99m sestamibi exercise scintigraphy: a new method for change rate mapping

In order to quantitatively assess the extent and severity of myocardial ischemia by Tc-99m sestamibi exercise myocardial scintigraphy, we developed a new method of change rate (CR) mapping and examined its efficiency. CR was calculated to divide the counts per pixel in the stress polar map by that in the rest polar map at each corresponding pixel. The CR map showed the CR values at each pixel. To correct the differences between the stress and rest images for the dose of Tc-99m sestamibi administered, the mean counts per pixel in the stress polar map and the rest map were adjusted to the same level. Regarding the regions in which the CR value was less than 1 as ischemia, we compared the abilities of the CR map and the polar map to detect coronary artery stenosis in 5 patients with angina pectoris. The sensitivity for coronary artery stenosis was 80% in the CR map, and 40% in the polar map. The specificity for both was 75%. We concluded that the CR map was effective in assessing the extent and severity of myocardial ischemia in Tc-99m sestamibi exercise myocardial scintigraphy.

Feasibility of simultaneous dual-isotope myocardial perfusion acquisition using a lower dose of sestamibi

The feasibility of simultaneous dual-isotope myocardial perfusion imaging was assessed using a ca. 12 mCi dose of technetium-99m sestamibi (MIBI) and ca. 3 mCi thallium-201. Planar and single-photon emission tomographic (SPET) data from 40 patients (41 studies) imaged with both a single- and a dual-isotope protocol were analyzed. Rest injected 201T1 (pure-T1) images were acquired using 20% windows at 70 and 166 keV about 15 min after the 201T1 injection. Patients were then stressed, and at peak stress 99mTc-sestamibi was injected. About 30 min later 99mTc data were recorded with a 20% window center at 140 keV, and simultaneous 201T1 (dual-T1) data were recorded with a single 20% window centered at 80 keV. Total myocardial counts based on SPET data in the dual-T1 images were increased by 18.61% +/- 2.91% (SEM) (range: -12.8% to 84.1%) compared to pure-T1 images. Region of interest analysis revealed the greater increase in counts in the apical region and the least in the lateral wall. Pure T1 and dual-T1 images were visually evaluated for image quality (IQ) on a five-point scale (0 = unacceptable to 4 = excellent). Dual-T1 IQ was lower than that of pure-T1 in 61% of cases, and similar in 37% (12% of the pure-T1 and 41% of the dual-T1 images fell into the 0 and 1 categories). Thallium perfusion abnormalities were of similar extent in 70% of segments, less severe in 18%, and more severe in 12%. There was an inverse correlation with patient weight, such that patients weighing more than 180 lbs had substantially worse images than those below this cutoff value. While dual-tracer images are of lower quality, they are interpretable if the patient is not severely overweight.

Dipyridamole technetium 99m sestamibi myocardial tomography for preoperative cardiac risk stratification before major or minor nonvascular surgery

The value of dipyridamole technetium 99m sestamibi (MIBI) tomography for preoperative cardiac risk stratification was assessed in 285 consecutive patients being considered for nonvascular surgery. A "major" (n = 140) or "minor" (n = 89) nonvascular procedure was later done in 229 of these patients < or = 4 months after dipyridamole testing. Perioperative cardiac events (unstable angina, acute ischemic pulmonary edema, nonfatal myocardial infarction, or cardiac death) occurred in 11 (8%) patients undergoing major nonvascular surgery and 1 (1%) undergoing a minor procedure. The only clinical or scintigraphic variables associated with significantly increased perioperative cardiac risk in patients having major surgery were Goldman class > or = II, an abnormal MIBI scan, and a fixed perfusion defect. In these patients, cardiac events occurred in 1% of those who had a normal MIBI study, 14% of those with an abnormal scan (p < 0.01), 12% with a reversible MIBI defect (p = 0.29), and 17% with a fixed MIBI defect (p < 0.01). In the 60 patients whose Goldman class was > or = II, only an abnormal MIBI study and a fixed perfusion defect were associated with incremental risk of a perioperative cardiac event. The incidence of perioperative cardiac events in these patients was 4% with a normal MIBI scan, 27% with an abnormal study (p < 0.05), 24% with a reversible MIBI defect (p = 0.45), and 37% with a fixed defect (p < 0.01). Event rates were low in patients having minor nonvascular surgery; none of the 25 with a normal MIBI study and only 1 of the 64 with an abnormal scan had a perioperative cardiac event (p = not significant (NS). We conclude that dipyridamole MIBI tomography can provide important prognostic information in patients having major nonvascular surgery. A normal MIBI study indicates a low risk of perioperative cardiac events, whereas an abnormal study in patients with Goldman class > or = II undergoing major surgery is associated with significantly increased risk. The prognostic value of MIBI tomography in patients at low clinical risk undergoing minor surgery is limited.

Dipyridamole technetium-99m sestamibi myocardial tomography in patients evaluated for elective vascular surgery: prognostic value for perioperative and late cardiac events

Dipyridamole thallium-201 myocardial imaging can provide information regarding risk of perioperative cardiac events in patients being considered for vascular surgery. The value for this purpose of myocardial imaging with technetium-99m sestamibi (MIBI), a radiotracer with biokinetic and imaging properties different from thallium-201, has not been established. To this end the prognostic value of dipyridamole MIBI tomography for perioperative and late cardiac events was evaluated in 229 consecutive patients being considered for elective vascular surgery. Vascular surgery was done < or = 3 months after testing in 197 of these patients. Perioperative cardiac events (cardiac death, nonfatal myocardial infarction, unstable angina, or ischemic pulmonary edema) occurred in 9 (5%) patients. The rate of such events was 3% in patients with normal MIBI results, 5% in those with abnormal results, and 6% in patients with a reversible MIBI defect (both p = NS). When patients with abnormal MIBI results who had preoperative cardiac interventions (coronary revascularization or an increase in antiischemic medical therapy) were compared with with those who did not, no significant differences in the occurrence of perioperative cardiac events were found between these two groups either. A group of 172 medically treated patients who survived vascular surgery and did not have a nonfatal perioperative cardiac event was then monitored (mean 21 +/- 14 months) for the occurrence of a serious late cardiac event (nonfatal myocardial infarction or cardiac death). Event-free survival (Mantel-Cox) was significantly less in patients with abnormal studies compared with those with normal scan results. Late cardiac events occurred in 26 (15%) patients, with those having an abnormal MIBI result showing a significantly greater event rate than those with normal results (26% vs 4%, p < 0.0001). The rate of late cardiac events was 33% in patients with a reversible MIBI defect (p < 0.001) and 23% in those with a fixed defect (p < 0.03). Independent Cox multivariable predictors of increased risk of late cardiac events were a history of diabetes mellitus (relative risk [RR] 2.2, 95% confidence interval [CI] 1.0 to 4.9), an abnormal MIBI study (RR 3.7, 95% CI 1.2 to 11.4), and a reversible MIBI defect (RR 2.7, 95% CI 1.2 to 6.1). We conclude that, although its ability to assess increased perioperative cardiac risk remains uncertain, dipyridamole MIBI tomography does provide important prognostic information regarding the risk of serious cardiac events in patients having vascular surgery. The presence of an abnormal MIBI result, specifically one demonstrating a reversible perfusion defect, is associated with significantly increased risk.

Comparison of pressure-derived fractional flow reserve with poststenotic coronary flow velocity reserve for prediction of stress myocardial perfusion imaging results

The physiologic importance of coronary stenoses can be assessed indirectly by stress myocardial perfusion imaging or directly by translesional pressure and flow measurements. The aims of this study were to compare myocardial fractional flow reserve (FFRmyo), a recently proposed index of lesion significance derived from hyperemic translesional pressure gradients, with directly measured poststenotic flow velocity reserve for the prediction of myocardial perfusion stress imaging results in corresponding vascular beds. Poststenotic coronary flow velocity (0.018-inch guide wire) and translesional pressure gradients (2.7F fluid-filled catheter) were measured at baseline and after intracoronary adenosine (12 to 18 micrograms) in 70 arteries (diameter stenosis: mean 56% +/- 15%, range 14% to 94% by quantitative angiography). Coronary flow reserve was calculated as the ratio of hyperemic to basal mean flow velocity. FFRmyo was calculated during maximal hyperemia as equal to 1-(hyperemic gradient [mean aortic pressure-5]), where 5 is the assumed central venous pressure. Positive and negative predictive values and predictive accuracy for reversible stress myocardial perfusion abnormalities were computed. There was a significant correlation between pressure-derived FFRmyo and distal coronary flow reserve (r = 0.46; p < 0.0001). The strongest predictor of stress myocardial perfusion imaging results was the poststenotic coronary flow reserve (chi square = 33.2; p < 0.0001). The correlation between stress myocardial perfusion imaging and FFRmyo was also significant (chi square = 8.3; p < 0.005). There was no correlation between stress myocardial perfusion imaging and percentage diameter stenosis (chi square = 2.9; p = 0.10) or minimal lumen diameter (chi square = 0.47; p = 0.73). A poststenotic coronary flow reserve of < or = 2 had a positive predictive value of 89% for regionally abnormal myocardial perfusion imaging abnormalities, whereas the positive predictive values of FFRmyo and angiographic percentage diameter stenosis were only 71% and 67% respectively. In conclusion, the predictive value of poststenotic coronary flow velocity reserve for stress-induced myocardial perfusion abnormalities exceeds that of the translesional FFRmyo. These findings should be considered when applying these techniques for clinical decision making in the assessment of coronary stenosis severity.

Prognostic value of predischarge dipyridamole technetium 99m sestamibi myocardial tomography in medically treated patients with unstable angina

Recently developed unstable angina clinical practice guidelines have recommended risk stratification with dipyridamole thallium-201 myocardial imaging in patients at "intermediate" pretest clinical risk who cannot exercise maximally. The prognostic value of predischarge dipyridamole technetium 99m sestamibi (MIBI) tomography has not been assessed in this clinical setting. To this end, 128 medically treated patients with unstable angina at intermediate pretest clinical risk underwent follow-up for 16 +/- 11 (mean +/- SD) months after predischarge intravenous dipyridamole MIBI tomography. An abnormal MIBI scan result was present in 99 patients (77%), of whom 47 had one or more reversible and 76 had one or more fixed perfusion defects. Cardiac events occurred in 68 (53%) patients after dipyridamole testing: recurrent unstable angina (n = 36), nonfatal acute myocardial infarction (n = 6), or death (n = 26). A cardiac event occurred in 10% of patients with normal MIBI tomography results compared with 69% of those with abnormal results (p < 0.01). Event rates associated with specific perfusion defects were similar (reversible = 68%; fixed = 71%) and were greater than rates in patients without defects (both p < 0.05). Clinical variables associated with increased risk of cardiac events by univariate analysis included a history of congestive heart failure, prior myocardial infarction, and diabetes mellitus (all p < 0.05). Independent multivariable predictors (Cox proportional hazards model) of any cardiac event were an abnormal result of MIBI scan (relative risk [RR] = 4.3, 95% confidence interval [CI] 1.5 to 12.0) and a reversible (RR = 1.8, 95% CI 1.1 to 2.9) or a fixed perfusion defect (RR = 2.9, 95% CI 1.6 to 5.4).(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise technetium-99m myocardial tomography for the risk stratification of men with medically treated unstable angina pectoris

The prognostic value of predischarge maximal exercise stress testing with technetium-99m sestamibi (MIBI) myocardial tomography was assessed in 126 consecutive men hospitalized with a diagnosis of unstable angina pectoris who were medically stabilized. None had coronary revascularization for < or = 6 months after testing. Over a mean follow-up of 12 +/- 7 months (range 1 to 29), 35 patients (28%) had a cardiac event--nonfatal acute myocardial infarction (n = 6), cardiac death (n = 5), or rehospitalization for unstable angina (n = 24). Any type of cardiac event occurred in 12% of patients with normal MIBI scans, compared with 39% of those with an abnormal MIBI scan (p < 0.001) and 60% of those with a reversible perfusion defect (p < 0.0001). Only 2% of patients with normal scans had either a nonfatal myocardial infarction or cardiac death, compared with 14% of those with abnormal MIBI scans (p < 0.05) and 25% with a reversible defect (p < 0.001). A fixed perfusion defect was not associated with increased cardiac risk. With use of multivariable Cox proportional-hazards modeling, the only scintigraphic variable with independent predictive value was the presence of a reversible MIBI defect, with a relative risk of 3.8 (95% confidence interval 1.6 to 8.6, p < 0.05) for any cardiac event, and 19.2 (95% confidence interval 2.2 to 167.0, p < 0.05) for a nonfatal myocardial infarction or cardiac death. Cardiac event-free survival was also significantly decreased in patients with a reversible perfusion defect (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dipyridamole on myocardial perfusion and function using technetium-99m MIBI

Myocardial perfusion imaging with dipyridamole is an accepted method for diagnosing coronary artery disease. However, the simultaneous effect of dipyridamole on perfusion and function in the detection of coronary artery disease has not been studied extensively. The aim of this study was to investigate this effect using technetium-99m methoxy isobutyl isonitrile (Tc-MIBI) imaging. Twenty-eight patients with proven coronary artery disease participated in a 2-day protocol (rest and then 0.56 mg/kg dipyridamole i.v.) using Tc-MIBI for first-pass radionuclide ventriculography followed by SPECT imaging. Fifteen patients (54%) demonstrated a decrease in left ventricular ejection fraction from rest to dipyridamole and/or wall motion abnormality, while 21 patients (75%) showed abnormal perfusion by dipyridamole MIBI SPECT imaging. Concordance between perfusion and function was 65%. Correlation for one-, two- and three-vessel disease (coronary angiography) to perfusion versus function were: 54% vs. 38%, 80% vs. 60% and 80% vs. 80%, respectively. Left ventricular dysfunction using dipyridamole was noted in patients with multivessel disease, and with multi-reversible perfusion filling defects. We conclude that dipyridamole in combination with Tc-MIBI for assessment of perfusion and function serves as a valuable tool to identify patients with multivessel disease and a high amount of myocardium at risk.

Comparison between 201Tl and 99mTc sestamibi uptake during adenosine-induced vasodilation as a function of coronary stenosis severity

BACKGROUND

Myocardial uptake of either 201Tl or 99mTc-sestamibi (sestamibi) is known to plateau at high coronary flow rates. However, few direct comparisons have been made between these tracers to determine what effect differences in the uptake plateau for the two tracers may have on the detection of coronary stenoses of various severities.

METHODS AND RESULTS

Twenty-two dogs were instrumented with flow transducers on the left anterior descending (LAD) and circumflex (LCx) arteries. In 6 nonstenotic dogs, adenosine was infused directly into the LAD, whereas 16 dogs with either critical (n = 7) or mild (n = 9) LAD stenoses received an intravenous infusion. At peak flow, 201Tl (0.5 mCi), sestamibi (5 to 8 mCi), and radiolabeled microspheres were injected simultaneously. Five minutes later, dogs were killed, and ex vivo imaging of heart slices and gamma-well counting of multiple myocardial samples was performed. Neither 201Tl nor sestamibi uptake increased in direct proportion to flow. In the 6 nonstenotic dogs, a fivefold increase in LAD flow increased 201Tl and sestamibi uptake by only 202 +/- 6% and 138 +/- 4%, respectively (P < .0001). In the dogs with critical stenosis, the ratios of stenotic to normal activity by well counting for 201Tl (0.37 +/- 0.05) and sestamibi (0.53 +/- 0.06) underestimated the microsphere-determined flow disparity (0.17 +/- 0.03) (P < .005), but the degree of underestimation was greater for sestamibi (P = .001). Similarly, in the dogs with mild stenosis, the stenotic-to-normal ratio for 201Tl (0.62 +/- 0.04) approximated the flow ratio (0.43 +/- 0.04) better than sestamibi (0.79 +/- 0.03) (P < .0001). Sestamibi defects, however, were visually identifiable on the images of the myocardial slices. By image quantification, sestamibi defect magnitude (LAD-to-LCx count ratio) in the critical stenosis group (0.62 +/- 0.05) was significantly less than in the mild stenosis group (0.80 +/- 0.02) (P < .01).

CONCLUSIONS

Thus, with adenosine-induced hyperemic flow, both 201Tl and sestamibi significantly underestimated the magnitude of the flow disparity between stenotic and normal perfusion beds. The degree of underestimation was greater for sestamibi. The clinical implication of these experimental findings for vasodilator perfusion imaging remains to be determined, since factors such as greater redistribution and scatter with 201Tl could offset its advantages.

Myocardial sarcoidosis. Clinical value of technetium-99m sestamibi tomoscintigraphy

STUDY OBJECTIVE

The presence of defects on rest thallium 201 myocardial scintigraphy, reversible after dipyridamole infusion, was already demonstrated in myocardial localization of sarcoidosis. The present study compared the respective efficiency of a new tracer of myocardial blood flow, 99mTc sestamibi (sestamibi), vs thallium 201 (TI) for the diagnosis and follow-up of myocardial sarcoidosis.

METHODS

Quantitative single photon emission computed tomography (SPECT) was performed in 37 consecutive patients with confirmed sarcoidosis and clinical suspicion of myocardial localization. Three successive scans were performed in all patients within the same day: rest TI SPECT, rest sestamibi SPECT, and dipyridamole sestamibi SPECT. Thirteen patients were reinvestigated after 3 months of corticosteroid therapy. The size and intensity of the defects were compared using a computerized quantitative analysis of bull's eye.

RESULTS

At rest, sestamibi SPECT is more sensitive than TI, demonstrating significantly larger defects (28.1 +/- 13.2% vs 17.2 +/- 12.8% of bull's eye area, p < 0.001) and detecting abnormalities in seven more patients (24 vs 17). All patients with abnormal TI scans also had sestamibi abnormalities. After dipyridamole infusion, sestamibi defects decreased significantly (28.1 +/- 13.2% vs 15.2 +/- 12.3%, p < 0.001). This improvement correlated with the evolution of sestamibi SPECT performed in the 13 patients reinvestigated after corticosteroid therapy (r = 0.85, p < 0.001).

CONCLUSIONS

We conclude that sestamibi SPECT is suitable for the diagnosis of myocardial sarcoidosis and represents an objective tool for the follow-up. The improvement after vasodilatation supports the hypothesis of reversible abnormalities in most of these patients and accurately predicts corticosteroid efficiency.

Correlation of pharmacological 99mTc-sestamibi myocardial perfusion imaging with poststenotic coronary flow reserve in patients with angiographically intermediate coronary artery stenoses

BACKGROUND

The physiological assessment of angiographically intermediate-severity stenoses remains problematic. Functional measurements of poststenotic intracoronary Doppler coronary flow reserve can be performed in humans but have not been correlated with hyperemic myocardial perfusion imaging or angiographic data in this patient population.

METHODS AND RESULTS

Thirty-three patients undergoing diagnostic quantitative coronary angiography (QCA) for assessment of intermediate-severity coronary artery disease (mean QCA percent diameter stenosis, 56 +/- 14%) were studied. Proximal and distal poststenotic Doppler coronary flow velocities were measured (left anterior descending coronary artery, 16; right coronary artery, 10; left circumflex artery, 7 patients) before and during peak maximal hyperemia with intracoronary adenosine (8 to 12 micrograms). Intravenous pharmacological stress (adenosine, 20 patients; dipyridamole, 13 patients) 99mTc-sestamibi tomographic perfusion imaging was performed within 1 week of coronary flow-velocity studies. kappa statistics were calculated to measure the strength of correlation among coronary flow velocities, perfusion imaging data, and QCA results. QCA stenosis severity (abnormal, > or = 50% diameter stenosis) and poststenotic Doppler coronary flow reserve (ratio of abnormal distal hyperemic to basal flow, < or = 2.0) were correctly correlated in 20 of 27 patients (74%; kappa = .48). QCA stenosis severity and 99mTc-sestamibi imaging (abnormal if one or more reversible myocardial segments were present in the poststenotic zone) were correlated in 28 of 33 patients (85%; kappa = .63). 99mTc-sestamibi imaging results agreed with the basal (nonhyperemic) proximal-to-distal velocity ratio (normal, < 1.7) in 15 of 31 patients (48%; kappa = .17). The strongest correlation occurred between hyperemic distal flow-velocity ratio measurements and 99mTc-sestamibi perfusion imaging results in 24 of 27 patients (89%; kappa = .78). All 14 patients with abnormal distal hyperemic flow-velocity values had corresponding reversible 99mTc-sestamibi tomographic defects. More reversibly hypoperfused segments were present in patients with abnormal poststenotic hyperemic flow-velocity ratios (abnormal, 2.4 +/- 0.7 segments; normal, 0.6 +/- 1.0 segments; P < .05). The number of poststenotic myocardial 99mTc-sestamibi perfusion defects was correlated with the QCA percent cross-sectional area reduction (P < .02) and with minimal luminal diameter (P < .05) of intermediate-severity coronary artery stenoses.

CONCLUSIONS

Two technologically diverse functional measures of stenosis severity--Doppler-derived poststenotic hyperemic intracoronary flow reserve and vasodilator stress 99mTc-sestamibi myocardial perfusion imaging--are highly (89%) correlated. The physiological assessment of coronary stenoses of angiographically intermediate severity may be improved by the use of these techniques.

Prognostic value of dipyridamole technetium-99m sestamibi myocardial tomography in patients with stable chest pain who are unable to exercise

Unlike dipyridamole testing with thallium-201, the ability of technetium-99m sestamibi (MIBI) myocardial imaging to evaluate risk of later cardiac events has not been established. In this study, the prognostic value of dipyridamole MIBI myocardial tomography (same-day, rest-stress protocol) was assessed in 534 patients with stable chest pain consistent with angina pectoris. During follow-up (mean 13 +/- 5 months), 58 patients (11%) had a major cardiac event--nonfatal myocardial infarction (n = 14) or cardiac death (n = 44). A history of congestive heart failure, prior myocardial infarction or diabetes mellitus, and either a reversible or fixed myocardial perfusion defect on MIBI scans were univariate and multivariate predictors of increased cardiac risk. Cardiac events occurred in 2% of patients with normal MIBI scans, compared with 15% with abnormal scans, 17% with reversible perfusion defects and 16% with fixed defects (all p < 0.01). Relative risks (univariate Cox analysis) associated with an abnormal MIBI scan, a reversible perfusion defect and a fixed defect were 8.4 (95% confidence interval [CI] 2.6 to 26.8), 1.9 (95% CI 1.1 to 3.2) and 2.4 (95% CI 1.4 to 4.3), respectively. Patients with any kind of perfusion abnormality (reversible or fixed) had a significantly lower cardiac event-free survival than those with normal scans (all p < 0.0001). It is concluded that, as with thallium-201 myocardial scintigraphy, a normal MIBI scan is associated with low cardiac risk, whereas dipyridamole-induced myocardial perfusion defects identify patients with significantly increased risk.

Myocardial viability in patients with chronic coronary artery disease. Comparison of 99mTc-sestamibi with thallium reinjection and [18F]fluorodeoxyglucose

BACKGROUND

99mTc-sestamibi and thallium imaging have similar accuracy when used for diagnostic purposes, but whether sestamibi provides accurate information regarding myocardial viability in patients with chronic coronary artery disease has not been established. Since there is minimal redistribution of sestamibi over time, it may overestimate nonviable myocardium in patients with left ventricular dysfunction, in whom blood flow may be reduced at rest.

METHODS AND RESULTS

We studied 54 patients with chronic coronary artery disease with a mean ejection fraction of 34 +/- 14%. Patients underwent stress/redistribution/reinjection thallium tomography and, within a mean of 5 days, same-day rest/stress sestamibi imaging using the same exercise protocol and with patients achieving the same exercise duration. Of the 111 reversible thallium defects on either the redistribution or reinjection study, 40 (36%) were determined to be irreversible on the rest/stress sestamibi study, whereas only 3 of 63 irreversible thallium defects despite reinjection (5%) were classified to be reversible by sestamibi imaging. The concordance regarding reversibility of myocardial defects between thallium stress/redistribution/reinjection and same day rest/stress sestamibi studies was 75%. A subgroup of 25 patients also underwent positron emission tomography (PET) studies with 15O-labeled water and [18F]fluorodeoxyglucose (FDG) at rest after an oral glucose load. As in the overall group of 54 patients, there was concordance between thallium and sestamibi imaging regarding defect reversibility in 51 of 73 regions (70%). In the remaining 22 discordant regions (30%), 18 (82%) appeared irreversible by sestamibi imaging but were reversible by thallium imaging. Myocardial viability was confirmed in 17 of 18 regions, as evidenced by normal FDG uptake (10 regions) or FDG/blood flow mismatch (7 regions) on PET. These regions were present in 16 of the 25 patients studied (64%). We then explored methods to improve the sestamibi results. First, when the 18 discordant regions with irreversible sestamibi defects were further analyzed according to the severity of defects, 14 (78%) demonstrated only mild-to-moderate reduction in sestamibi activity (51% to 85% of normal activity), suggestive of predominantly viable myocardium, and the overall concordance between thallium and sestamibi studies increased to 93%. Second, when an additional 4-hour redistribution image was acquired in 18 patients after the injection of sestamibi at rest, 6 of 16 discordant irreversible regions (38%) on the rest/stress sestamibi study became reversible, thereby increasing the concordance between thallium and sestamibi studies to 82%.

CONCLUSIONS

These data indicate that same-day rest/stress sestamibi imaging will incorrectly identify 36% of myocardial regions as being irreversibly impaired and nonviable compared with both thallium redistribution/reinjection and PET. However, the identification of reversible and viable myocardium can be greatly enhanced with sestamibi if an additional redistribution image is acquired after the rest sestamibi injection or if the severity of reduction in sestamibi activity within irreversible defects is considered.

Dipyridamole technetium 99m sestamibi myocardial tomography as an independent predictor of cardiac event-free survival after acute ischemic events

BACKGROUND

A total of 137 consecutive patients with recent uncomplicated myocardial infarction (n = 31) or unstable angina (n = 106) were studied to determine the relative prognostic value of predischarge clinical risk stratification and intravenous dipyridamole stress sestamibi (MIBI) myocardial tomography in patients unable to exercise maximally after an acute ischemic coronary event.

METHODS AND RESULTS

Patients were followed up after the index study for 10 +/- 5 months (range 1 to 23 months) to ascertain cardiac events that occurred in 20 patients (15%): nonfatal myocardial infarction (n = 5) or cardiac death (n = 15). Cardiac event rates were 35% in patients with a recent myocardial infarction and 8% in the group with unstable angina (p < 0.001). Patients with these cardiac events had more frequent abnormal MIBI study results, fixed defects, and reversible plus fixed (combined) defects (all p < 0.05). The univariate relative risk of death or myocardial infarction associated with an abnormal MIBI study was 6.0 (95% confidence limits 0.8 to 44.7). Multivariate stepwise logistic regression models identified an abnormal MIBI study and either fixed or reversible MIBI defects as being predictive of death or myocardial infarction (all p < 0.05). The Mantel-Haentzel 1-year cardiac event-free survival rate was excellent in 27 patients with a normal MIBI single-photon computed emission tomographic scan (100%) but significantly reduced in the 110 patients with an abnormal MIBI study (80%; p < 0.05 vs normal subjects). The presence of combined MIBI defects was associated with the poorest event-free survival rate (66%; difference not significant vs fixed or reversible defects only).

CONCLUSION

We conclude that predischarge dipyridamole MIBI tomography provided independent prognostic information in this population of patients who were unable to exercise after a recent acute ischemic coronary event.

Preoperative diagnosis of coronary artery disease in patients with valvular heart disease using technetium-99m isonitrile tomographic imaging together with high-dose dipyridamole and handgrip exercise

Forty-seven consecutive patients (mean age 61 +/- 8 years) referred for cardiac catheterization due to moderate to severe aortic (n = 30) or mitral (n = 17) valvular heart disease were examined by technetium-99m isonitrile tomography together with a high-dose dipyridamole infusion (0.7 mg/kg) and handgrip stress. Tomography did not identify coronary artery disease (CAD) in 3 of the 21 patients with angiographically proven disease (sensitivity 86%) and suggested false positive results in 5 of the 26 without the disease (specificity 81% and negative predictive accuracy 88%). No patient without angina pectoris and with negative scintigraphy (n = 14) had angiographically significant (greater than or equal to 50% diameter stenosis) CAD. Overall vessel sensitivity was 63%, and specificity was 92%. The frequency of side effects during the dipyridamole-handgrip test was only 7%. No serious complications occurred during stress tests. Thus, technetium-99m isonitrile tomographic imaging, together with high-dose dipyridamole and handgrip exercise, is a useful noninvasive method in excluding significant CAD in patients with valvular heart disease.

Usefulness of technetium-99m-MIBI and thallium-201 in tomographic imaging combined with high-dose dipyridamole and handgrip exercise for detecting coronary artery disease

Forty-two patients with known stable coronary artery disease, referred for coronary angiography, were examined with technetium-99m-hexakis-2-methoxy-2-methylpropyl-isonitrile (MIBI) tomography combined with a high-dose dipyridamole infusion (0.7 mg/kg) and handgrip stress. MIBI tomography was unable to show coronary artery disease only in 2 patients, thus yielding a sensitivity figure of 95%. MIBI tomography correctly identified 27 (82%) of 33 stenotic lesions (greater than or equal to 50% diameter stenosis) of the left anterior descending artery, 17 (61%) of 28 of those of the left circumflex artery, and 28 (90%) of 31 of those of the right coronary artery. The overall vessel sensitivity was 78%. The computed lumen diameter stenoses were more advanced in cases detected than in those not detected with MIBI tomography: 87 +/- 14 vs 76 +/- 14% (p less than 0.01). The 50 to 69% stenoses did not show any tendency to produce less positive findings than those with greater than or equal to 70% stenoses. In the subgroup of 21 patients who also presented for thallium scintigraphy, the overall diseased vessel identification rate was 76% for thallium tomography and 83% for MIBI tomography (p = not significant). Minor noncardiac side effects related to the dipyridamole-handgrip test occurred only in 5% of 63 study sessions. A high-dose dipyridamole combined with isometric exercise is a safe stress method, and when used during scintigraphy, MIBI tomography is at least as efficient a tool as thallium tomography in detecting diseased vessel territories in patients in coronary artery disease.

Technetium 99m sestamibi in the assessment of chronic coronary artery disease

Extensive work has already been performed with regard to both planar and single photon emission computed (SPECT) technetium 99m sestamibi studies. Before widespread application of optimized acquisition and processing methods, clinical results between 99mTc sestamibi and thallium 201 were remarkably similar. It is anticipated that as techniques for 99mTc sestamibi planar and SPECT imaging become optimized, improvements in sensitivity and specificity for detection of coronary artery disease, over those observed with 201TI, might be forthcoming. This expectation is based on the improved image quality inherent in the use of the 99mTc agent with its higher count rate and higher energy. This improvement in image quality may be a principal reason for laboratories to switch from 201TI to 99mTc sestamibi imaging. It is anticipated that, with improved imaging characteristics, it will be easier for the average community hospital to obtain higher quality planar or SPECT imaging using 99mTc sestamibi rather than 201TI. In addition to improved image quality, the characteristics of 99mTc sestamibi allow gated planar or SPECT perfusion images to be obtained. It has been suggested that stress-gated SPECT sestamibi studies may provide all the information contained in a stress-rest nongated 99mTc sestamibi study, thereby potentially increasing patient throughput, a major concern with SPECT. Throughput can also be increased by using dual-isotope approaches with rest 201TI and stress technetium sestamibi acquisitions, employing either separate or simultaneous imaging with which the entire study can be accomplished in less than 2 hours. With simultaneous dual-isotope acquisition, camera time can be reduced by 50%. Finally, 99mTc sestamibi offers the advantage of the ability to perform first-pass exercise ventricular function and SPECT myocardial perfusion studies with a single injection of tracer. Regarding the assessment of myocardial viability, results to date suggest a very high degree of concordance between 201TI and 99mTc sestamibi studies using either planar or SPECT acquisition techniques. Correlative rest studies with both tracers will be of particular interest, as will preoperative and postoperative and position emission tomography correlation studies.

Technetium-99m sestamibi in chronic coronary artery disease: the European experience

Since the introduction of technetium-99m methoxy-isobutyl isonitrile (Tc-99m sestamibi) in Europe, there has been a growing interest in its use. Several European multicenter trials have been conducted to evaluate this new agent in relation to the traditional perfusion marker thallium-201, and other studies are in progress to understand the use of this perfusion marker for the diagnosis of coronary disease, for use in conjunction with pharmacologic vasodilation, for use in the assessment of ventricular function and wall motion and for the assessment of interventions.